1. Field of the Invention
This invention relates in general to communication of data between electronic modules, and in particular to an electro-optical means for communicating data between modules.
2. Description of the Prior Art
Conventional electronic processing equipment, such as used in aircraft control systems, uses numerous circuit boards or modules containing electronic circuitry. Each circuit board or card has a large number of mechanical connections at its base or bottom for connecting into a backplane, which receives a number of modules. The backplane has wiring and circuitry to provide power to the modules, to transmit digital data on parallel data buses and serial data lines, and to transmit discrete and analog signals between the modules.
The electrical connections to the modules are a major source of failure in such equipment because of connector pin and socket wear, corrosion, contamination, and mechanical damage. Furthermore, the nature of the electrical connector failures is such that they are often intermittent in nature and thereby difficult to locate and correct.
Attempts have been made in the past to reduce the number of electrical connections to modules. Light transmit and receive diodes have been used in modules to interface to purely optical backplane devices fabricated using either fiber-optic or other optical wave guides to divide light emitted by the transmit diodes on one module and deliver portions of the light energy to corresponding receive diodes on the other modules. Such optical backplane devices are difficult to fabricate in such a manner as to permit adequate and uniform distribution of optical energy to receiving modules. Because the optical power must be divided, such devices are highly vulnerable to losses in optical connectors.
Also, electro-optical backplanes have been devised in which the signals are transmitted between electronic modules and backplanes by conventional electric means and then converted to optical form in the backplane at each module location for optical transmission of data to conversion devices located in the backplane at each other module. Such electro-optical backplanes face the problems of providing uniform light division between modules and the normal problems associated with electrical connectors. Furthermore, if failures occur in such backplanes, replacement or repair of such backplanes normally involves major disassembly of the equipment because of the bottom of the module locations used for such backplanes.